adobe flash builder 4: css type selectors are not supported in components spark.components.Label

Question

Hiya.

I created a new MXML component that contains some labels and the following style:

<fx:Style>
    @namespace s "library://ns.adobe.com/flex/spark";
    @namespace mx "library://ns.adobe.com/flex/mx";
    @namespace local "*";
    s|Label {
        font-size:12;
        font-weight:bold;
        color:white;
    }
    #timeLeftHGroup {
        left:30;
        top:12;
    }

I get the following warning at the s|Label line:

CSS type selectors are not supported in components: 'spark.components.Label'    

Well.. the CSS code does work! it did change the color, make the text bold and changed the font size to 12, so why do i get this warning ?